Process for stabilization of copper treated oils



Patented May 20, 1941 I UNITED STATES PATENT *OF L PROCESS FOR STABILIZATION TREATED onls or cornea.

' -Walter A. Schulze, Bartlesville, kla., and Graham H. Short, Phillips, -Tex., assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing.

Original application November 9, 1938, Serial No. 239,731.

Divided and this al plication May 28, 1940, Serial No. 337,735

color formation. It is customary, therefore, to,

subject said impure oil toa purifying treatment in order to remove the impurities or to convert them to less objectionable forms, forexample, the conversion of mercaptans to disulfides.

2 Claims. (Cl. 19630) agents, to remove said copper from the oil, thereby delaying or preventing deterioration.

The methods of treatment for the removal or.

conversion of mercaptans make use of variouschemical processes, and of these processes, one of the most satisfactory is the process utilizing copper, salts of copper, or solutions containing copper'salts. I

However, subsequent to treatment with copper-containing reagents, it has been found that many hydrocarbon oils require further treatment or stabilization. This condition is due tothe fact thatsaid unstable oils retain from theircontact with copper reagents, extremely small quantities of oil-soluble copper compounds.

These traces of copper compounds remaining in the oil are responsible forthe marked acceleration of reactions which lead to the formation in said oil of color, gum, resinous deposits'and polymers; these deteriorative changes seriouslyimpair such properties of the oil, tent and octane number:

One object of this invention is to efiect the removal of traces of copper compounds from hydrocarbon oils. 1

Another object 'of this invention is to prevent the deterioration of hydrocarbon oil which has been treated with copper reagents by the removal from said oil of small amounts of retainedoil soluble copper compounds responsible for aforesaid deterioration.

A further object of this invention is the production of hydrocarbon oil of good color and stable with respect to gum formation subsequent to treatment with copper-containing reagents.

A further object of this invention is the treatment of .oil which retains traces of copper comas color, gum conconsisting of those reagents which will effectively Another object of this invention is to provide a step in the sweetening of hydrocarbon oil with copper reagents whereby the sweetened oil is stabilized against deterioration by the removal therefrom of retained copper salts.

Another object of this invention is the conversion of oil-soluble copper compounds present in hydrocarbon oil as a result of sweetening with copper reagents to.oil-insoluble compounds, said conversion resulting in complete separation of the insoluble copper compounds from the oil. Schulze and Frey in U. S. Patent No. 1,980,555

described a method for stabilizing an oil'treated with copper and which exhibited discoloring and/or formation of resinous matter, polymers 1 and oxidation products; that is, a method of stabilizing the oil by bringing it in contact with an alkaline sulphide solution subsequent to treating with the copper reagent. 3'

We have not discovered that copper treated oils may be stabilized by means other than the alkaline sulfide solution referred to above and that these means involve certain improvements and advantages.

which must be met to produce stabilized oils. This discovery, likewise makes it possible to divide treating agents into two groups, the first group i remove the hydrocarbon oil-soluble copper compounds and thereby stabilize the oil, and the second group consisting of those reagents which will not remove suflicient quantities of the copper compounds-to stabilize the oil. We have found that copper mercaptides increase in solubility in the oil with increasing I molecular weight of the mercaptans. Copper methyl mercaptide is the most insoluble of. all the copper mercapti'des and-isalmost totally insoluble in hydrocarbon oils. Copper ethyl meroaptide, the next number in the series, is a little more soluble, yet its actual solubility figure is' P unds subsequent to swe tening wi h C p In other words, wehave'established that the This discovery is extremely im-' I portant in that it clearly defines the conditions 7 prolonged contact with copper methyl mercapconcentration of copper from a saturated solution of copper methyl mercaptide in hydrocarbon oil is too low to cause deterioration of the oils. On the otherhand, we have found that if the hydrocarbon ls saturated with respect to copper ethyl mercaptide, the concentration of copper is just suflicient to cause a slow depreciation in the said properties of the oil. Thus, we have established that there is a critical value for copper concentration in the oil, above which deterioration will occur, and below which the oil will be stable as regards gum and color formation in storage.

This improved process'of stabilization depends on the effective removal of traces of copper compounds from the contaminated hydrocarbonoil by treating said oil to completely convert the hydrocarbon oil-soluble copper compounds into compounds whose solubility is less than the sol- .these more insoluble compounds from the hydrocarbon oil, the deterioration due to dissolved copper compounds in the oil is prevented.

Since the deterioration of oil is accelerated in a catalytic manner by dissolved copper'salts, it

solutions, or by the addition to the oil of controlled amounts of ethyl mercaptan.

In order to explain more exactly the criterion by which the stabilization of copper-containing -oil is judged, the relative solubilities of the copper compounds encountered may be considered.

The sulfides of copper are the most insoluble compounds of the metal. The mercaptides by reason of analogous structure exhibit similar solubilities in water, but are slightly more soluble in oils due to the organic nature of the alkyl or aryl group present in the mercaptide molecule.

The sulfides of copper have a solubility of about 0.00033 gram per liter of water and an infinitesimal solubility in hydrocarbon oils; the solubility of copper methyl mercaptide is approximately 0.000003 gram per liter of cracked naphtha, or about one-hundredth the solubility of copper sulfide in water. These solubility figures ar based on extremely sensitive colorimetric tests, especially devised to indicate the presence and concentration of copper in hydrocarbon oil.

The following table shows the approximate solubilities of copper salts in oils, or the extent to which oil-soluble copper compounds are formed by contact of the oils with said copper salts for a follows that copper salts more insoluble than 24 hour period.

. Table I Dissolved Oil-soluble copper Copper salt Hydrocarbon oil copper gompounds Grams per 1000 cc. 4 Parts per million oil Copper oxide Doctor-sweet cracked naphtha. Greater than 1 0. 0003 (approx.) Copper carbonate (basic) d 0. 0003 (approx.) Copper hydroxide 0. 0003 (approx) Copper phosphate 0. 0003 (approx.) Copper cyanide (KCN sol 0. 0003'(approx.) Copper silicate 0 0003 (approx Copper sulfite 0. 0003 (approx Copper-n-butyl-mercaptlde 0. 0003 (approx.) Copper-t-butyl-mercaptide 0' 300 Copper-ethyl-mercaptide 00003 possess marked resistance to oxidation processes Ab which would change said insoluble copper compounds to more active forms which would be injurious to the oil.

Oil-soluble copper compounds which may be formed in complex hydrocarbon oil mixtures, particularly in petroleum dis'tillates, are usually mercaptides or salts of acidic components such as cresylic and naphthenic acids. Such conipounds may be more soluble than copper ethyl mercaptide, and likewise may not be removed from an oil in which said compounds are dissolved unless the method of treating or stabilization forms therewith copper compounds less soluble thancopper ethyl mercaptide. For example, after a cracked naphtha has been in contact with copper oxide, copper carbonate or copper phosphate, sensitive tests show the presence of traces of copper remaining in the naphtha, whereas a portion of the same naphtha after may be removed by adding thereto a controlled 70 amount of methyl mercaptan to convert the more soluble copper compounds into the less soluble copper methyl mercaptide. Complete removal of the copper is--not efiected by treatment of the oil with caustic soda, carbonate or phosphate 76 It will be seen from the values listed in Table I that complete removal of copper from an oil may not be accomplished by contacting said oil with a reagent to form any of the copper salts listed. This fact is based on experimental data which proves that the deterioration of anoil due to dissolved copper is not prevented unless the copper content of said 011 is reduced to a value less than 0.1 p. p. m. as shown in Table II.

Table II- Color On A r Hydrocarbon oil Dlssolved ina l after mt 32;;

copper color days stor storage age West 'Itexascracked Partsper million gasol l0. +25 l6 Dark brown.

D 1 +25 10 D0. Do 0.1 +25 +12 --16 color. Do Less than 0.1.. +25 +23 +21 color. Do Zero +25 +23 +21 color.

has of the practice of my invention,

EXAMPLE I A sample of cracked gasolin which had been, sweetened by treatment with a solution containing cupric chloride was separated from the copper reagent and divided into two parts. One part was stored without further treatment. To the other portion was added a solution of methyl mercaptan in sulfur-free hexane solution, the quantity added being sufiicient to cause the gasper compound and an excess remained. Portions of this gasoline were then treated with U various reagents to form copper salts less soluble than copper ethyl mercaptide. Samples of each portion of gasoline stabilized with the various reagents were then stored for comparison with a 1 mercaptide. The tabulation of results is given olineto have a methyl mercaptan content of 1 below:

' Table in I I rig Color Color N o. Gasoline sample Copper t t; I inal after Bite! t color 1 7 days days storage storage 1 Cracked gasoline-no additional treatment" "Q; Negative I +24 +22 2 CiI-Iagked gasoline-saturated with solid copper-ethyl-mercap- Positive, approx. +24 +16 1 e. p. p. m. 3 #2 sample-added 0.006 per cent methyl mcrcaptan followed by. Negative,lessthan +24 +22 +21 1 water wash. I 0.1 p. p. m.

4 #2 sample-plus 2 per cent sour vapor recovery gasohne contains-. do +24 +21 ing 0.01 per cent methyl mercapta n. #2 sample-intimately contacted with alkahne aqueous solu- +24 +22 tion of dithizone. I 6 #2 samplecontacted with ammomacal solution of alpha- +24 +22 I benzoinoxime. I I p 7 #2 sample-contacted with aqueous solution of th10nal1de +24 +22 8 #2 sample-contacted with aqueous solution of 5.7-d1bromohy +24 +22 droxyquinoline. I I I I 9 #2 sample-contacted with ammomacal solution of dlethyldido +24 thiocarbonate. I I

0.003-weight per cent. After the addition of the mercaptan, the gasoline was allowed to stand for two hours, after which it was washed with water and stored. The results of this stabilizingt'reatment are shown below:

- the critical. value for. allowable copper concenorigi Color I Gasoline samples Copper test 11:11 I ggg Appearance after color 'Istomge days storage Cracked gasoline unstabilized Positive, greater than 1 p. p. m.- +24 16 Dark brown, gummy. Cracked gasoline plus 0.003 percent Negative, less than 0.1 p. p. m +24 V+23 +22 color.

methyl mercaptan. I

This gasoline was doctor sweet; no trace of mercaptan after two days.

EXAMPLE II A sample of the same gasolinedescribed in Example I was similarly treated except that the stabilizing reaction was brought about by the stabilization are illustrated below:

This vapor recovery g-astration in oil which is stable with regard to'color' and gum formation I We claim: I

' 1. In the process of sweetening hydrocarbon oil in storage is thus disclosed.

- with copper reagents, the step of stabilizing the sweetened oil toprevent deterioration due to retained oil soluble copper salts which comprisesadding a small quantity of a comprising thionalide.

2. The process as in claim 1 in which thestastabilizing agent.

. r l Color t I Origi- Appearance Gasoline sample Copper test nal gigg y after 30 days color storage storage Cracked gasoline-copper treatedunstabilized Positive, greater than 0.1 p. p. In +24 -16 Dark brown, Cracked gasoline-copper treated plus 2 per cent Negative, less than 0.1 p. p. m +24 +23 +22 color.

(vol.) 0! sour vapor recovery gasoline. I I I This gasoline was doctor sweet.

7 EXAMPLE III -To a sample of doctor sweet cracked'gasoline was added solid copper ethyl mercaptide and shaken until the oil was saturated with the cop-- WALTER A. 'SCHULZE'. GRAHAM H..SHORT. 

